Conventionally, many kinds of methods of manufacturing silicon that is used as a raw material of a semiconductor and a solar battery for power generation have been known. Some of the above methods have already been implemented industrially.
For instance, one of above methods is called a Siemens method. In this method, a silicon rod that has been heated up to a deposition temperature of silicon by energizing is disposed in a bell jar, and trichlorosilane (SiHCl3) and monosilane (SiH4) are made to come into contact with the silicon rod together with a reducing gas such as hydrogen to deposit silicon.
This method, by which high purity silicon can be obtained, is implemented industrially as a general method. However, since silicon is deposited in a batch system, it is necessary to repeat for each batch a series of processes such as installing of a silicon rod that is a seed, energizing, heating, depositing, cooling, and extracting of the silicon rod, and cleaning of the bell jar, thereby requiring complicated operations.
On the other hand, as a method capable of continuously manufacturing polycrystal silicon, a method using an apparatus shown in FIG. 1 is proposed (see Patent documents 1 and 2). This silicon manufacturing apparatus is provided with a reaction vessel 2 made of a carbon material, a raw gas supply port 5 that is disposed on an upper side of the reaction vessel 2 and that supplies the chlorosilanes and hydrogen into the reaction vessel 2, and a high frequency heating coil 7 disposed on the periphery of the reaction vessel 2 in a closed container 1.
The reaction vessel 2 is heated by an electromagnetic wave emitted from the high frequency heating coil 7 disposed on the periphery thereof. A section from a bottom end portion 2a of the reaction vessel 2 to a specified height (a region enclosed by the alternate long and two short dashes line in the figure: reaction portion 3a) is heated up to a temperature at which silicon can be deposited.
The chlorosilanes supplied from the raw gas supply port 5 is made to come into contact with the heated inside face of the reaction vessel 2 to deposit silicon to the inside face of the reaction portion 3a. 
In the apparatus shown in the figure, the reaction portion 3a is heated up to a temperature less than a melting point of silicon at which silicon can be deposited, and silicon is deposited in a solid state. The reaction portion 3a is then heated up to a temperature equivalent to or higher than a melting point of silicon, and the part or whole of a deposited substance is molten, dropped from an opening of the bottom end portion 2a, and recovered in a cooling recovery chamber (not shown) disposed in a dropping direction.
Moreover, there is another method in which the inside face of the reaction vessel 2 is heated up to a temperature equivalent to or higher than a melting point of silicon to deposit silicon in a molten state, and a silicon molten solvent is continuously dropped from an opening of the bottom end portion 2a of the reaction vessel 2 and is recovered.
Since a silicon deposition in a region other than the inside face of the reaction vessel 2 in the closed container 1 causes an operation to be prevented, the sealing gas supply port 8 for supplying a sealing gas such as hydrogen and an inert gas is formed for instance at a region in which silicon must be prevented from being deposited, such as a region around the bottom end portion 2a of the reaction vessel 2, in order to prevent a silicon deposition.
Moreover, an apparatus similar to one shown in FIG. 1 is used for other applications as a reaction apparatus of the chlorosilanes for reacting the chlorosilanes and hydrogen by a hydrogen reducing reaction. For instance, an apparatus similar to one shown in FIG. 1 is used for reducing silicon tetrachloride to trichlorosilane in order to recover a raw gas for manufacturing polycrystalline silicon.
Even in this case, silicon is deposited to the reaction portion 3a heated up to a temperature at which a hydrogen reducing reaction occurs by an electromagnetic wave emitted from the high frequency heating coil 7. Silicon tetrachloride is then reduced to trichlorosilane by making silicon tetrachloride and hydrogen that have been supplied from the raw gas supply port 5 to come into contact with an inside face of the reaction portion 3a to which silicon has deposited. A gas after the reaction is recovered in a portion outside the closed container 1 through an opening of the bottom end portion 2a of the reaction vessel 2.    Patent document 1: Japanese Laid-Open Patent Publication No. 2003-2627    Patent document 2: Japanese Laid-Open Patent Publication No. 2002-29726
In a silicon manufacturing apparatus as shown in FIG. 1, a reaction vessel 2 is made of a carbon material. Silicon coats a carbon face of the inside face of the reaction portion 3a, or a silicon carbide film formed by a reaction between silicon and carbon coats the carbon face. However, a perforated carbon face is exposed on a non reaction portion 3b (a region enclosed by the alternate long and short dash line in the figure) on the upper side of the reaction portion 3a. 
Since the chlorosilanes such as trichlorosilane is a molecule having an extremely large viscous resistance, a person with an ordinary skill in the art has never thought conventionally that such the chlorosilanes penetrate a pipe wall at the non reaction portion 3b of the reaction vessel 2 and leak externally. In practice, such a phenomenon has never occurred conventionally.
However, in the case in which a mole ratio of hydrogen in a raw gas is increased, trichlorosilane is effectively decomposed and a deposition efficiency of silicon is improved. Therefore, in the case in which a mole ratio of hydrogen to trichlorosilane was increased and an amount of hydrogen exceeded a certain mole ratio, there was a phenomenon in which trichlorosilane together with hydrogen penetrated a pipe wall of the reaction vessel to leak externally.
In a silicon manufacturing apparatus described above, by shortening an inner diameter of the reaction vessel at the intermediate section and by making an internal shape of the reaction vessel complicated, a gas flow resistance change section such as an orifice and a curved pipe portion is formed in the reaction vessel, and a differential pressure is set between an inlet on the upper side and an outlet on the bottom end portion side in the reaction portion (a numeral 3a in FIG. 1), thereby improving a contact efficiency of a raw gas and accelerating a reaction.
However, in many cases, the above phenomenon in which the chlorosilanes such as trichlorosilane together with hydrogen penetrates a pipe wall of the reaction vessel to leak externally occurs in the case in which a differential pressure is applied inside the reaction vessel in particular.
In the case in which the chlorosilanes supplied to the reaction vessel penetrate a pipe wall and leak externally, an outside face of the reaction vessel and a heat insulating member installed outside the reaction vessel are deteriorated. In addition, in some cases, silicon is deposited to other members and apparatuses.
The present invention was made in order to solve the above described problems. An object of the present invention is to provide a reaction apparatus of the chlorosilanes sufficiently capable of suppressing that a raw gas such as the chlorosilanes supplied into the reaction vessel penetrates a pipe wall of the reaction vessel to leak externally.